A 3-year-old boy presents with self-mutilation, choreoathetosis, hyperuricemia, and intellectual disability. Enzyme deficiency responsible for this condition catalyses which reaction?
- A Conversion of hypoxanthine to IMP and guanine to GMP in the purine salvage pathway ✓
- B Conversion of xanthine to uric acid by xanthine oxidase
- C De novo synthesis of IMP from phosphoribosylamine
- D Adenosine deamination to inosine in lymphocytes
Correct answer: A. Conversion of hypoxanthine to IMP and guanine to GMP in the purine salvage pathway
Explanation
Lesch-Nyhan syndrome is caused by deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT), the salvage pathway enzyme that converts hypoxanthine to IMP and guanine to GMP using PRPP. Its deficiency leads to accumulation of PRPP and uric acid (via de novo synthesis and degradation), and also depletes GTP in the basal ganglia, causing neurological features. Self-mutilation is pathognomonic. Xanthine oxidase acts downstream, and ADA deficiency causes SCID without neurological features.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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